Yimei Du

Absrtact: Cardiovascular disease remains the leading cause of death worldwide. Previous studies have largely regarded immune cells as passive sources of inflammatory mediators, while paying insufficient attention to their intrinsic electrophysiological properties governed by ion channels and Ca2+ signaling. This review focuses on ion channels as upstream molecular switches that determine immune cell functional states, elucidating how they regulate membrane potential and intracellular Ca2+ dynamics to shape immune cell activation thresholds, effector intensity, phenotypic polarization, and spatial behavior, thereby constituting the core regulatory axis of the immune cell electrophysiological microenvironment. We then demonstrate how immune cells transmit their electrophysiological states to the myocardium through at least three distinct mechanisms: (1) Ca2+-dependent inflammatory mediator secretion remodeling cardiomyocyte ion channels; (2) direct electrocoupling between resident immune cells and the cardiac conduction system via Cx43 gap junctions; and (3) chronic immune activation progressively establishing arrhythmogenic substrates. We further illustrate how these electrophysiological mechanisms couple immune cell electrophysiological function to cardiac pathology across distinct disease contexts, including myocardial infarction, arrhythmias, and myocarditis. Finally, we discuss the translational potential of targeting immune cell ion channels as a therapeutic strategy for cardiac diseases, and identify key unresolved challenges. Research into immune cell electrophysiology holds significant implications for deepening our understanding of cardiac disease mechanisms and developing innovative therapeutic strategies. Keywords: Immune cell electrophysiology; Ion channels; Calcium signaling; Myocardial remodeling; Cardiac arrhythmia; Atrial fibrillation; Heart failure; Myocardial infarction

The alkaloid higenamine, a non-selective β-adrenergic receptor agonist, not only exerts beneficial effects in heart diseases but also induces severe cardiotoxicities, including malignant arrhythmias. Although its actions are attributed to β-adrenergic signaling activation, this mechanism does not explain its potent and often fatal arrhythmogenic effects. Here, we challenge this notion by demonstrating, for the first time, that higenamine’s primary toxic action results from direct, agonist-like activation of L-type calcium channels, independent of adrenergic signaling. Using high-resolution optical mapping, patch-clamp electrophysiology, and confocal calcium imaging in rat cardiac preparations, we demonstrate that higenamine induces profound intracellular calcium overload, leading to triggered activity and malignant electrical instability. Crucially, we uncover an unexpected protective role for the canonical β-adrenergic pathway: instead of triggering toxicity, it acts as a compensatory mechanism that promotes calcium sequestration, serving as a physiological brake against overwhelming calcium influx. This reveals a hierarchical mechanism whereby direct channel modulation constitutes the primary insult, with receptor signaling acting as a homeostatic response. Our findings redefine the molecular basis of higenamine poisoning and provide a mechanistic mandate for a clinical paradigm shift: establishing calcium channel inhibition, rather than β-blockade, as the first-line targeted therapy for this widely accessible yet poorly regulated toxin.

Mechanical hyperalgesia is a primary symptom of clinical pain; there remains a therapeutic challenge for severe mechanical and chronic forms of neuropathic pain. The 34-amino-acid neuropeptide GsMTx4, isolated from Tarantula spatulata, was identified as a selective inhibitor of mechanosensitive channels and shown to reduce mechanical hyperalgesia and neuropathic pain in rats. We previously reported two types (type I and type II) of short peptides derived from GsMTx4 that mimicked the inhibitory action of GsMTx4 on a mechanosensitive BK (SAKca) channel. In this study, we investigated whether these short peptides alleviate mechanical hypersensitivity, a major symptom of neuropathic pain. The synthetic type I peptide 01 (Pept 01) was derived from loop2+loop3 of GsMTx4, whereas type II Pept 02, Pept 03 and, Pept 04 were derived from loop 2 of GsMTx4. Carrageenan-induced inflammatory pain was induced in rats and mice, while the chronic constriction nerve injury (CCI) model was established in rats. We showed that administration of short peptides (270 μg/kg, i.p.) selectively inhibited mechanical pain in rats but failed to impact thermal or cold hyperalgesia. Interestingly, the antihyperalgesic effects of these peptides were comparable to those of morphine; however, they were resistant to the μ-opioid receptor antagonist naloxone and lacked morphine-induced side effects, e.g., tolerance and conditioned place preference (CPP). Among them, Pept 03, which contained only one Trp (Trp1) at the head and an additional Arg (Arg11, corresponding to Arg18 in GsMTx4) at the end of the peptide, most potently alleviated mechanical hyperalgesia. Genetic deletion of the TRPV4 gene in mice mostly abolished the analgesic effect of Pept 03. In oocytes expressing TRPV4 channels, application of Pept 03 or Pept 01 inhibited GSK101- or hypotonicity-activated TRPV4 currents in a dose-dependent manner. These results suggest that TRPV4 channels may serve as a direct target for the short peptides in alleviating mechanical pain. This study identifies several natural toxin-based peptides as promising non-opioid analgesics, paving the way for the development of selective and potent painkillers to treat mechanical pain.

Postoperative atrial fibrillation (POAF) frequently arises after cardiac surgery and is associated with atrial inflammation and remodeling. The sterile pericarditis (SP) model reproduces this condition in rats, providing a valuable platform to investigate inflammation-induced atrial electrophysiology. This protocol describes the preparation of Langendorff-perfused rat hearts after SP induction and the use of simultaneous dual optical mapping to record transmembrane voltage and calcium transients. Hearts are stained with the voltage-sensitive dye RH237 and the calcium indicator Rhod-2 AM, while contractility is suppressed using blebbistatin to minimize motion artifacts. High-speed imaging enables spatiotemporal mapping of atrial action potentials and calcium dynamics during controlled pacing protocols. Quantitative parameters include action potential duration, conduction velocity, calcium transient duration, time to peak, and alternans magnitude. The method allows precise assessment of atrial conduction heterogeneity, electro-calcium coupling, and arrhythmia vulnerability under inflammatory stress. This visualized approach provides a reproducible and versatile platform for studying POAF mechanisms and testing pharmacological or genetic interventions that target atrial remodeling.

Myocardial ischemia-reperfusion (IR) injury remains a major clinical challenge, often exacerbating cardiac damage despite timely reperfusion. The transient receptor potential vanilloid 4 (TRPV4), a Ca ²⁺ -permeable non-selective cation channel, has emerged as a key mediator of IR injury. TRPV4 is widely expressed in cardiomyocytes, endothelial cells, and immune cells, and its activation under ischemic stress promotes Ca ²⁺ overload, oxidative stress, inflammation, and endothelial dysfunction. Upregulation and membrane translocation of TRPV4 during IR aggravates intracellular Ca ²⁺ influx, sarcoplasmic reticulum Ca ²⁺ leak, and mitochondrial impairment. TRPV4 also amplifies reactive oxygen species (ROS) production, impairs antioxidant defenses, and triggers inflammatory signaling. Additionally, TRPV4 contributes to cardiomyocyte apoptosis, pyroptosis, and possibly ferroptosis. Preclinical studies demonstrate that selective TRPV4 antagonists (e.g., HC-067047, GSK2193874) significantly reduce infarct size, preserve cardiac function, suppress arrhythmias, alleviate myocardial stunning, and prevent coronary no-reflow. The age-related upregulation of TRPV4 further highlights its therapeutic relevance in elderly patients. Targeting TRPV4 thus represents a promising strategy to mitigate multifactorial myocardial injury and improve outcomes following reperfusion therapy.